Highly transparent, mechanically strong, recyclable, and flame-retardant vanillin-modified poly(urethane-urea) elastomers via dynamic oxime-urethane bonds and hydrogen bonds

Motivated by sustainable development strategies, the design of repairable and recyclable polyurethane or polyurea elastomers has garnered significant attention. However, integrating superior mechanical properties with self-healing and recycling capabilities of elastomers remains a formidable challenge. Furthermore, the inherent flammability limits their practical applications. In this study, we introduced a novel approach by using lignin-derived vanillin as a bio-based raw material to synthesize the phosphorus-containing monomers (TMPOH and HVPOH) with dynamic oxime bonds. Then, the poly(urethane-urea) elastomers (PUA-TMPOH and HVPOH) based on dynamic oxime-urethane bonds and hydrogen bonding interactions were prepared. PUA-TMPOH exhibited excellent mechanical properties, including the impressive tensile strength of 50.9 MPa and high elongation at break of 811.9 %. The incorporation of dynamic oxime-urethane bonds imparted exceptional self-healing, reprocessing, and recyclability to the material. During the dissolution recycling process, the mechanical properties of the PUA-TMPOH and HVPOH remained above 95 %, effectively extending the service life. The introduction of phosphorus-containing structures also significantly enhanced the fire safety performance of elastomers. In cone test, both PUA-TMPOH and PUA-HVPOH demonstrated an obvious decrease in peak heat release rate (PHRR) and total heat release (THR) with decreases of 23.6 % and 30.5%, respectively, compared to PUA-0. This work provides a feasible pathway for developing high-performance, bio-based, dynamically flame-retardant polyurea elastomers.